This invention relates to a rotational mechanism disposed within a fluid passageway and more particularly to a silencer (muffler) provided with a rotational mechanism disposed within a noisy air or gas stream for effectively muffling the noise thereof. The invention, and further relates to a rotary pump (including a rotary fan and called simply rotary pump hereinafter) of capacity the or displacement type provided with a rotational mechanism disposed within a fluid passageway which is positively driven by external driving means for transporting the fluid.
Silencers are generally mounted in an exhaust gas pipe of an internal-combustion engine for damping the noise of the exhaust gas, and the structural gist of the silencers of such type resides in (1) making the diameter of the silencer larger than that of the exhaust gas pipe or narrowing the passage of the exhaust gas for expanding and compressing the exhaust gas to diminish the force thereof, and (2) obtaining repeated sound reflections of the exhaust gas by means of bending or winding the passageway, for thereby effectively damping the exhaust gas noise.
In recent years the noise of enlarged engines of model planes, particularly those with engines controlled by wireless radio means, has become a source of a kind of noise problems. For the model planes with large engines silencers of the rotary impeller type (which are provided with a simple wind wheel) are employed.
Such conventional silencers are relatively of large size for the size of the engine and occupy a large space, so miniaturization is required from the standpoint of weight reducing and fine appearance. However, the requirement for miniaturization and the convenient reduction in noise preventive effect caused by the miniaturization are two contradictory problems.
Capacity type pumps or displacement pumps are generally machines for transporting fluid under pressure by means of the action of pushing away or displacing the fluid with a piston, plunger, rotor, or the like. Such pumps are generally classified into reciprocation and rotation types. Pumps of the rotation type are characterized by the portion which pushes away or displaces the fluid rotating. Gear pumps, screw pumps, cam pumps, vane pumps, etc., are examples of the rotation type. Among displacement type pumps are included those with two shafts and a mechanism wherein a pair of rotors are mounted in a casing on parallel axes offset from each other for being rotated in opposite directions for transporting fluid. Pumps of this type are preferably utilized where it is required that the amount of fluid to be discharged be moved in proportion to pump rotor speed. The discharge of this type of pump is substantially proportional to the rotation of the rotors. This type has generally been believed to be not preferred for transporting large amounts of fluid because of such problems as (1) requiring precise machining in the manufacturing thereof, (2) being relatively large and heavy in weight, and (3) being unsuitable for high speed rotation.